- Aerodynamic jump
- A small vertical shift of the shot caused by crosswind. Its direction depends on the twist direction.
- BC – ballistic coefficient
- A number that tells how well the bullet overcomes air resistance. The higher it is, the less the bullet slows down. It refers to a model: G1 or G7.
- Click
- One detent of the scope turret. Usually 0.1 mil or 1/4 MOA.
- Coriolis
- A small deflection of the shot caused by the Earth's rotation. It matters only at very long range.
- Density altitude
- A way to say, with a single number, how dense the air is. It combines pressure, temperature and humidity.
- Drop
- How far the bullet falls below the line of sight at a given range, due to gravity.
- Elevation
- The vertical correction to dial on the turret to compensate for drop.
- G1 and G7
- Two reference projectiles used to express BC. G7 describes modern long-range bullets better.
- Line of sight
- The straight line from the eye, through the scope, to the target.
- Maximum ordinate
- The highest point of the trajectory above the line of sight. It tells you whether the shot clears an obstacle.
- Mil (milliradian)
- An angular unit: 1 mil equals 10 cm at 100 meters, and 1 meter at 1000 meters.
- MOA
- Minute of angle: about 2.9 cm at 100 meters.
- Muzzle velocity
- The speed of the bullet as it leaves the barrel. Measure it with a chronograph: it is the input that weighs most on the calculations.
- PBR
- Point Blank Range: the distance span in which the shot stays inside the vital zone of the target without corrections.
- Quick Wind Factor
- A number for your rifle that lets you estimate the wind correction from memory.
- Range Card
- The card with the targets of a stage or a position and their corrections.
- Range tolerance
- How far off your range estimate can be while still hitting the target.
- SG – gyroscopic stability
- Tells how well the bullet is stabilized by its spin. It depends on twist rate, bullet and air.
- Shooting angle (inclination)
- The inclination of the line of fire from horizontal, uphill or downhill. The steeper it is, the less the bullet drops relative to the line of sight.
- Speed Drop Factor
- A number for your rifle that lets you estimate drop from memory, starting from the range.
- Spin drift
- The drift caused by the bullet's spin: with a right-hand twist the shot goes slightly to the right.
- Stage
- A match or training exercise: positions, targets, time and order of fire.
- Supersonic, transonic, subsonic
- The bullet slows down: above the speed of sound it is stable, around it (the transonic zone) it can become unstable, below it it is subsonic.
- Time of flight
- The time the bullet takes to reach the target. It matters for wind and for moving targets.
- Wind by the clock
- Wind direction given as the hours on a clock face: 12 o'clock from the front, 3 o'clock from the right, 9 o'clock from the left.
- Windage
- The horizontal correction: wind, spin drift and Coriolis.
- Zero
- The range at which point of aim and point of impact coincide. Usually 100 meters.
Every term is also explained inside the app, with the "?" button next to the input.
